1. Field of the Invention
This invention relates to a portable bridge system that can be assembled on site, particularly in remote locations such as timbering locations. The bridge is formed from at least a pair of substantially rectangular bridge platforms or panels that are positioned in side-by-side relationship to form the bridge span. The invention includes end locking plates integral with, and mounted on, at least two corners of the bridge platform to lock the platforms together at opposite ends of each platform. An end locking plate is aligned with, and is bolted to, an adjacent end locking plate of the adjacent bridge platform. At least one of the pair of adjacent bridge platforms further includes a plurality of shear plates, or keys, spaced apart along the side length of the bridge platform and fixed thereto. These shear plates mate with the corresponding side length of the adjacent bridge platform and provide resistance against relative shear forces, or movement, between the platforms in a transverse, i.e., a downward direction.
2. Description of Related Art
Portable bridge systems formed from separate bridge platforms, or panels, are known in the art. One such bridge system, as further described hereinbelow, has been devised by West Virginia University. Such bridge systems are formed from a plurality of bridge platforms that are rectangularly shaped and include side channels and, in some cases, end plate channels. The bridge platform surface itself is formed from a plurality of laminates of lumber, typically each lumber board being 6 to 12 inches thick and 11/2 inches wide. The wooden boards are sandwiched between the steel side channel members and compressed between the side channel members by tensioning rods or stressing bars that extend transversely across and through the bridge platform, from side channel to side channel, and through each of the wooden boards. In forming a bridge from these platforms, a pair of such platforms are positioned in side-by-side relationship and are connected to each other, on site, by inserting a plurality of long connecting bolts, or tensioning rods, each having a length greater than the overall side-to-side width of the two bridge platforms, through holes or openings extending through the side channels and wooden boards. These elongated bolts are then tensioned on the job site to retain the bridge platforms to each other. In addition, and during the connecting bolt insertion process prior to tensioning, a plurality of wooden shear blocks, having holes or openings therethrough, are positioned between the side channels of the platforms during the assembly. The connecting bolts are threaded through each wooden shear block. These wooden shear blocks assist in preventing transverse movement or sliding of one bridge panel with respect to the adjacent bridge panel.
The overall portable bridge system as described above has a number of disadvantages. For example, installation of the bridge becomes quite labor intensive at the job site. The adjacent bridge platforms or panels must be carefully aligned with each other so that the elongated and cumbersome connecting bolt may be inserted through the connecting hole openings, first through one platform, then through the wooden shear blocks, and then through the next platform. Because the width of each platform may be approximately six feet (excluding the wooden shear blocks), thus making the overall width of the pair of platforms in excess of twelve feet, the alignment of the platforms and shear blocks, and the insertion of the connecting bolts, are extremely difficult. As can be appreciated, depending upon the particular terrain over which the bridge is to be formed, it may be difficult to precisely align the openings of each bridge platform with the adjacent bridge platform so as to be able to insert the elongated connector bolt through the rather substantial width of the two bridge platforms. In addition, insertion of the wooden shear blocks between the side channels of adjacent bridge platforms is time consuming and logistically difficult, particularly where the bridge is to be assembled at great heights, or over water, where access to the underside of the bridge platforms is difficult.